Synthesis and catabolism of complement and properdin proteins, surfactant lipid and protein and histamine will be measured in alveolar macrophages and organotypic lung cell cultures. The effects of agents that alter synthetic or catabolic rates of the specific lung cell products will be studied to determine whether there is independent or coordinate regulation of these functions. The mechanisms of catabolism and characterization of products of catabolism will be studied using immunochemical and physiochemical methods. The results of the proposed studies will serve to elucidate the basis for developmental and pathophysiological changes in some components of pulmonary host defenses and alveolar structure and function.